Telephone-transmitter.



G. L. GHISHOLM.

TELEPHONE TRANSMITTER. I

APPLICATION FILED JAN. 8, 1907.

Patented May 4, 1909.

CHARLES L OHISEOLM, OF MARYSVILLE, NEW BRUNSWICK, CANADA.

no. eaons i.

Specification of Letters Patent Patented May a, 1909.

v Application filed January 8, 1907. Serial No. 351,375.

Toyati whom it may concern: Be it known that. l, CHARLES L. Cnrsnomr,

a subject of the King of England. residing at lea-i svllle, New bitlllSWlCk, Canada," have.

invented a new and useful Telephone-Transnn tei, or which the following is a spec hcation.

The invention relates to acoustic instruments and particularly to telephone tiansmitters, the object in view being to provide such a construction and arrangement of parts as to prevent the formation of nodes in the diaphragm andcause the sound waves orjbeats to affect the diaphragm on truly concentric lines, thereby insuring the transmission of the message without interference or disturbance of secondary or false vibrations. To accomplish this it has been found necessary to provide the diaphragm with a comparatively narrow peripheral bearing upon which it is securely held in asuitable insulating bed, all of that portion of both surfaces of the diaphragm which is inside of the bearing being unobstructed withthe ex ception otthe single central'point of practically unconsidera'ble area upon which bears the contact pin or member through which the: vibrations, or the efiectsof the vibrations, are conveyedlto' the microphone; and

furtherit has been found necessary in order to prevent the, formationof secondary vibrations to place the diaphragm under stress or -tension toa degree, which will insure ample resistance to inducedvibrati'on or formation and caii'se' the wavesJor-beats of the dia phragm to be.- arranged on lines truly concentric with the'central point of contact and in order that the diaphragm thus peripherally supported with a narrow area of support and eing thus placed under a tension sufficient to eliminate the possibility of vibration except under the influence of sound Waves attacking the same or impingement upon the surface thereof, it ghas been foundnecessary to use a diaphragm of relatively small .diametenand great thickness as the extreme concaving or (lGl lGCtIOII Of the diaphragm from the true flat plane is not desir able. The intimate relations existing between the contact point and the diaphragm due tothe tension appliedto the diaphragm by means of the contact pin insuresthe true and accurate transmission of the impulses 'from the diaphragm to the contact point,

entirely eliminates the possibility of there bein -any separation or break between the and it will be understood that various changes in the form, proportions and minor details of construction may beresorted to without departing from the spirit-of the invention which is set forth in the" appended claims.

In the accompanying drawings :F igur'e 1 is a diagrammatical sectional view of a transmitter embodying the invention. Fig. 2 is face view of the same, the cap being omitted.

Similar numerals of reference indicate corresponding parts throughout the several figures of the drawings.

The diaphragm 1 is seated in a frame 2 as in the ordinary practice, it-being noted that the seat 3 is of small area so as to engage the diaphragm only at its periphery, the usual or any preferred bedf tbeing employed to em,- brace the periphery of the diaphragm. The ordinary or any preferred-microphone is represented by the numeral 5, and the contact pin 6 is reduced terminally to bear upon the surface of the diaphragm at its exact center, thus leaving all portions of both surfaces oi the diaphragm unobstructed except at this central point. justing the contact pin may be varied to suit the peculiarities of construction of the mimophone and related parts, but in the "form. illustratedin the drawing the screw 7 serves for the'purpose of advancingthe contact .pin to a greater or less-e'iteitt to place the diaphragm under the desired tenslonal stress with the etr'ect of insuring a relatively fixedv position of the diaphragm at its true center, and thereby insure the formation 0); sound waves or beats on truly concentriclines. It

has been found in practice that by-adpisting the contact-point to exert a greater or less pressure on the diaphragm, when the d1aphragm is or" a thickness or stifiness capable of resisting a consider-able pressure, the secondary or false tones or screeching, or-as it may more'properly be termed, harmonics,- can be entirely eliminated, and, therefore, bv

The means employed for ad.

operative relation betweenv the contact: pin

- also been propose of the tone and the recognizability, especially satisfactorily by establishing such-a relation adjusting the parts of a transmitter this coand the diaphragm can be'established' to-secure the desired result, slight variations in the thickness or rigidity .of the diaphragm being compensated for by the possibility of ad'ustment of the contact pin.

am aware of the fact that transmitters have been devised heretofore with various thicknesses of dia hragms and that it has (i to apply pressure to the contact pin sufficient to produce a concavoconvexity of the diaphra m, the diaphragm thus being in a sense cut, laut it will be noted that the object of this invention-is not to cause a concavo-convex construction of the diaphragm, but to use a diaphragm of a rigidity sufficient to resist a pressure of the contact pin which will be sufficient to eliminate false tones and insure the faithful reproduction of the waves impinging thereon, where: by the over tones which are so often lost in transmission and which form the character as to voices thereof may be preserved and transmitted. This can be accomplished between the rigidity'of the diaphra m and the stress of the contact pin as will p ace the diaphragm while flat and in position to properly receive the contactlof the sound waves under such a tension as to prevent-the form'a tion of nodes and hence of false notes and I harmonics.

I clann:.

tively thick and superficially unobstructed diaphragm having aperipheral support of Y diaphragm with the'bearing surface of pracs tically inconsiderable area, the diaphragm being of such thickness as to not sensibly dish under the pressure of the contact pin necessary to maintain the contact,

2. In a telephonic transmitter, 'a comparatively thick and rigid and superficially unobstructed diaphragm, and a microphonic element having a contact pin with a bearing surface of practically, inconsiderable area directly engaging but unsecured to said diaphragm,

In testimony that I claim the foregoing as my own, I have hereto affixed my signature in thep resence of two witnesses.

CHARLES L. CHISHOLMJ I Witnesses:

E. HUME TALBERT, W; J. DILLON.

. Y 1. In a telephonic transmitter, a compara- 

